SUGI 28 Systems Architecture Paper 283-28 SAS®, Linux/UNIX and X-WINDOWS systems Gady Kotler, Executive Information Systems Ltd., Herzlia, ISRAEL ABSTRACT Usually the host is a UNIX box and the client This paper will discuss features of the native is a PC machine but not necessarily. If one windowing system (called X-Windows) found uses a UNIX or Linux desktop box, then the on Linux/UNIX based systems and topics server side and the client side are both related to SAS® implementations on these implemented on the same box. Since X- systems. windows is an open standard, numerous implementations exists on virtually any As Linux/UNIX based servers and desktop machine ranging from hosts like UNIX, Linux, systems continue to evolve, we find it AS/400, DEC VAX, IBM MVS/VM and important to review the different ways to clients like PC’s, Macintosh, OS/2 and more. implement SAS on these platforms and to compare them to other alternatives such as Microsoft based NT/2000 servers and PC’s If we implement SAS using this model as an desktops or other thin clients implementations. example: the server machine is a powerful host, which is responsible for the I/O and The paper is aimed for SAS system number crunching. The client machine is administrators who would like to implement an responsible for displaying the SAS windows: open environment within their SAS Log, Out, Pgm, Explorer and AF windows installation. with results coming from the server over the network. X-WINDOWS BACKGROUND In this context, we can use any machine with X-windows have started its way on 1984 at a graphics capabilities residing on the network to project held at MIT called ATHENA. The display the application’s windows as long as project’s aim was to create a working there is a well defined protocol that can environment for displaying windows coming handle all requests coming from the server to from multiple incompatible hardware and display and manipulate the window’s contents. operating systems. The result was a truly open architecture that was hardware and vendor independent. The name ”X” was given to this X-windows is based upon such a protocol that windowing system since it’s the letter separates the application logic running on one following “W” which was given to an earlier machine from the presentation running on version. another machine. These two machines are communicating between them using the X By 1986, MIT has released for commercial use protocol. version 11 release2. Later on the development of this standard was handled over to a consortium of companies called X org. In the X-windows world the application knows (www.x.org). nothing about the end device that is being used to display its windows. Things like resolution, Today all UNIX vendors and Linux color schemes, mouse device, keyboard device distributors adopted this standard for the etc. are left for the client machine to handle. windowing system. The current release is X11R6.6 which can be downloaded freely from the above web site. The client side, on the other hand, knows nothing about the application that sends him X-WINDOWS INTERNALS requests for displaying windows and contents X-windows is a client-server model that inside the windows. The client side is capable separates the application logic from its GUI. to display multiple windows attached to This separation enables the transferring of the multiple applications running on multiple GUI part via a network from a host to a client. servers in the network. -1- SUGI 28 Systems Architecture Special topic: Client-Server terminology The terms “Server” and “Client” are being The X terminals were the first true graphical used in the X-windows context in a reversed thin client machines. X terminals first appeared manner than the way it is being presented in on the market during the late 80’s (When PC’s this paper. In X-windows terminology, the struggled to run DOS operating systems). “Server” side is a piece of software running on As the PC market evolved, and more powerful the “small” end-user machine (The machine CPU’s were embedded into the PC, many we usually call the client machine…). companies had found a way to implement the client side of the XLib protocol as an This “X Server” package serves requests to Microsoft’s windows application running as a display windows coming from “Clients” which software only solution. are the applications running on the “big” machine elsewhere on the network. (This “big” This trend had put an end to the traditional X machine is the machine we usually call the terminal market (While we can still see many “Server” or “Host” machine). of them working in many sites since they were very reliable machines with no mechanical Using this “Reversed” terminology, the X- parts which practically can function for ever). windows package that is installed on a PC is called “X server” packages … Today most of the X-windows terminals are implemented using a software solution running X-windows implementation is based upon under MS windows (95 and above) as yet several layers as follows. (Not all layers are another application on our desktop. While X- always implemented). windows application appear to us as a regular MS windows application, its underlying 1. The application. structure differs completely from any other MS 2. The Application development standards & windows application. toolkits 3. The Xlib protocol. Application Development standards & 4. The window manager. toolkits 5. The desktop environment. At the early days of the x protocol, no other layer was build on top of the Xlib and applications were written with direct calls to Xlib protocol functions of the Xlib protocol. Only later, more The first layer of an X-windows layers were defined to simplify the implementation is a very basic protocol that is development process. These additional layers being used to transmit request to open include toolkits and widgets libraries, which windows and to render the application help to standardize the look and feel of the contents. This protocol has also a mechanism applications. for sending back to the host keyboard and mouse events. Since Xlib protocol contains no definition of how the user’s desktop or application look and This well-defined protocol called “Xlib feel should be, users had started to ask for a protocol” is the first layer of any X-windows more unified desktop environment and more implementation. The Xlib protocol is a truly uniform look and feel for all thousands of X- open standard and its definition can be windows applications that were written. downloaded from X.org freely at no charge. This open source policy contributed to the As X-windows became more popular and was popularity of the Xlib protocol and created vast recognized as standard de-facto of the UNIX implementations of devices that can handle the industry, UNIX vendors began the X-windows client side of the Xlib protocol. war in order to gain control over this growing market. Special topic: X-Terminals Since early days of X-windows, vendors Sun Microsystems was trying to establish a developed devices called “X-Terminals”. standard called “Open-Look” for the look and These devices had a Monitor, Keyboard, feel of applications, while other vendors Mouse and a very small firmware that had the fearing that Sun might “Take Over” the X- X server code embedded into it and the CPU windows market with its own standards, power needed to render the Xlib protocol formed a group called OSF (stands for: Open functions. No need for an operating system, Software Foundation). The OSF group has disks or other devices. released a competitive standard for the look -2- SUGI 28 Systems Architecture and feel of applications called the Motif Look and feel. These standards established the foundation for a common look and feel of applications with the same widget set and the same rules for designing a window, borders, menus and other objects. (Eventually, Sun has adopted Motif). Special topic: SAS and X-windows standards SAS uses none of the standards widget sets to implement the look and feel of SAS windows. I believe it is done in order to keep the SAS Figure 1 – SAS running under MS look and feel of DMS and AF windows as windows without a window manager. compatible as possible to all other SAS implementation running on other platforms. As one can see from the above figure, all SAS If you’ll use SAS on different UNIX/Linux windows appear without a border, thus cannot platforms you’ll get the same look and feel of be removed or resized. SAS windows. The only difference you’ll be able to notice is the window manager style (see When working with PC’s X servers, you can below). choose MS windows as your window manager program. This technique is mostly In SAS V6 running on Solaris there was an recommended since it saves resources on your experimental user interface that implemented PC and LAN and integrates your X application the Open Look standards but there was no into one common behavior of windows. continuation for this project. Windows managers A window manager is a piece of software that handles all events arising from displaying your application’s windows along with other windows all on the same screen. For example, when a user moves a window from one corner of the screen to another position, this is an event that is being handled by the window manager. The application knows nothing about this event. Events like moving/hiding/resizing of windows are all being handled by the window manager.